According to vehicle safety regulations in some countries, such as United States, etc., a daytime running lamp (DRL) in a vehicle should be turned on during driving in order to improve safety. FIG. 1 shows a block diagram of a conventional DRL system 100 in a vehicle. As shown in the example of FIG. 1, the conventional DRL system 100 includes a DRL light source, e.g., a light emitting diode (LED) light bar 102, and a DRL controller 101 to control power to the LED light bar 102. The DRL controller 101 is coupled to an ACC power line (not shown). However, it is difficult to find the ACC power line in the vehicle and, as such, it is inconvenient to install the DRL controller 101 in the vehicle. Moreover, the DRL light source cannot be automatically turned off when position lamps (also known as parking lights) or a direction indicator lamp (also known as a turn signal) of the vehicle is activated; thus, the DRL light source might distract other drivers and keep them from noticing the activated position lamp or direction indicator lamp.